1 files changed, 54 insertions, 0 deletions
diff --git a/crates/tor-proto/src/tunnel.rs b/crates/tor-proto/src/tunnel.rs
new file mode 100644
index 000000000..f02b5794c
--- /dev/null
+++ b/crates/tor-proto/src/tunnel.rs
@@ -0,0 +1,54 @@
+//! Module exposing tunnel-related types shared by clients and relays.
+
+use std::sync::atomic::{AtomicU64, Ordering};
+
+use crate::circuit::UniqId;
+use derive_more::Display;
+
+/// The unique identifier of a tunnel.
+#[derive(Debug, Clone, Copy, Eq, PartialEq, Hash, Display)]
+#[display("{}", _0)]
+#[cfg_attr(feature = "relay", visibility::make(pub))]
+#[allow(unreachable_pub)] // TODO(#1447): use in ChanMgr's ChannelProvider impl
+pub(crate) struct TunnelId(u64);
+
+impl TunnelId {
+    /// Create a new TunnelId.
+    ///
+    /// # Panics
+    ///
+    /// Panics if we have exhausted the possible space of u64 IDs.
+    pub(crate) fn next() -> TunnelId {
+        /// The next unique tunnel ID.
+        static NEXT_TUNNEL_ID: AtomicU64 = AtomicU64::new(1);
+        let id = NEXT_TUNNEL_ID.fetch_add(1, Ordering::Relaxed);
+        assert!(id != 0, "Exhausted Tunnel ID space?!");
+        TunnelId(id)
+    }
+}
+
+/// The identifier of a circuit [`UniqId`] within a tunnel.
+///
+/// This type is only needed for logging purposes: a circuit's [`UniqId`] is
+/// process-unique, but in the logs it's often useful to display the
+/// owning tunnel's ID alongside the circuit identifier.
+#[derive(Debug, Clone, Copy, Eq, PartialEq, Hash, Display)]
+#[display("Circ {}.{}", tunnel_id, circ_id.display_chan_circ())]
+pub(crate) struct TunnelScopedCircId {
+    /// The identifier of the owning tunnel
+    tunnel_id: TunnelId,
+    /// The process-unique identifier of the circuit
+    circ_id: UniqId,
+}
+
+impl TunnelScopedCircId {
+    /// Create a new [`TunnelScopedCircId`] from the specified identifiers.
+    pub(crate) fn new(tunnel_id: TunnelId, circ_id: UniqId) -> Self {
+        Self { tunnel_id, circ_id }
+    }
+
+    /// Return the [`UniqId`].
+    pub(crate) fn unique_id(&self) -> UniqId {
+        self.circ_id
+    }
+}